400ex valve adjustment

Bibical.400 · #1 02-02-2011, 10:44 PM

Alright i bought this quad a week ago....99' 400ex, and the valves were tapping from the getgo. It has a stage one hot cam in it. From what im told cammed 400s are supposed to tap? Went for a little rip yesterday and all of a sudden they started tapping LOUD and the exhaust seemed to be louder. All ehaust pipes are bolted tight. Shut it off immediatly. The dude i bought it from said theres no plunger valve or whatever in it. What do i do? Still has compression and fires right up.

Bibical.400 · #2 02-02-2011, 11:50 PM

I found a valve adjustment guide on here that is thorough, saying it is alright to keep the stock adjustments of .005 & .006 with this cam, but it literally sounds like metal baseball bats slamming off each other when running/cranking. Any input would be awesome, thanks all.

90vfradam · #3 02-03-2011, 01:56 AM

HI
I would check all gaps on valves ,just to be safe..........
There are 2 things that could make that much noise- The timing chain will make a hell of alot of noise if it is worn--listen to some on you tube- sounds like valves but isnt....
The other possible thing is that when they put in new cams and left the decompression valve assembly off, it coul d be part of that rammbling around... I would lean towards the timing chain though ---that can make a helluva lot of noise...
Hope this helps

Bibical.400 · #4 02-03-2011, 02:10 AM

I plan on tearing into it tomorrow morning and checking the valves. It went from ticking loudly to ticking REAL loudly in a matter of a second. Could a timing chain do that?

90vfradam · #5 02-03-2011, 02:14 AM

Yes it will slap around, There are a couple of them on you tube who had the same issue as you, makes a racket, when you open it up you can check the spec on it...

Bibical.400 · #6 02-03-2011, 02:27 AM

Looked the videos up and that it probably it. How hard is it to fix and how much? Still checking the valves also. Thanks guys

90vfradam · #7 02-03-2011, 12:53 PM

The chain around $80, depends where you buy...
Use shop manual and it isnt that hard , just take your time...check tensioner while you are in there..

Bibical.400 · #8 02-03-2011, 02:54 PM

After some research, might as well upgrade to a crf450 chain right?

Here 2 help · #9 02-03-2011, 03:23 PM

Dittto on the tensioner. They can stick and quit taking up slack. Also, a scored piston will make the same ticking noise and it just gets worse with run time. Compression can be good and the piston might be bad. Who put the cam in? You almost never get valve noise in an OHC motor. My race bike runs .007 intake and .012 exhaust, but there is no valve noise. You might want to pull the cam cover off the motor and check the rocker arm pads. There is a lot of parts in that cover (rockers, sub-rockers, the shafts the parts pivot on). Don't forget to check that one of the cam sprocket bolts hasn't backed out and might be clipping something in the head or head cover. Good luck.